The etiology of chronic wounds is generally multi-factorial of which hypoxia is a common factor. Clinical conditions involving hypoxic wound include peripheral vasculopathy (diabetics, arteriosclerosis, etc.), post- operative recovery, and arterial hypoxia (e.g. pulmonary fibrosis or pneumonia, sympathetic pain response, hypothermia, major blood loss, cyanotic heart disease, high altitude). This proposal addresses the significance of O2 in wound healing of such cases. The proposal has two facets: understanding oxygen- sensitive mechanisms in the wound, and developing approaches for wound oxygenation. For the first time, the highly significant hemoglobin-based HBOC ("artificial blood") technology is being studied for wound oxygenation. The central hypothesis is that wound oxygenation is a key determinant of wound angiogenesis. Chronic ischemic wounds are typically hypoxic. While hypoxia acutely triggers the expression of angiogenic factors and responses, long-term hypoxia cannot sustain the formation of new functional vasculature resulting in wound chronicity. Correction of wound hypoxia supports healing. Aims 1 and 2 rest on the observation that hypoxia in mice impairs the healing of full thickness dermal wounds. Correction of hypoxia, restored wound closure. Aim 3 is based on similar observations in a pre-clinical swine model of ischemic wound. The following three aims are proposed: AIM 1. Characterize the effects of tissue oxygenation on the preparation for wound angiogenesis: i. Establish the effects of tissue oxygenation on wound closure;ii. Examine the effects of tissue oxygenation on the preparation for wound angiogenesis in the early inflammatory phase;iii. Test the role of hypoxia-inducible factor (HIF) in wound angiogenesis under conditions of hypoxia. AIM 2. Determine the mechanisms by which the state of tissue oxygenation influences wound angiogenesis in the late tissue-remodeling phase: i. Determine the significance of hypoxia-induced inhibition of dermal wound TGFbl;ii. Investigate the role of low wound-site NO production under conditions of limited O2. AIM 3. Test whether oxygenation of wounds influences full-thickness dermal wound healing in a pre-clinical swine model of ischemic wound: i. Test whether local application of O2 (gas-based and HBOC- based approaches) corrects full-thickness wound hypoxia;ii. Determine whether oxygenation accelerates wound closure;iii. Determine if correction of wound hypoxia facilitates angiogenesis and blood flow.